EUV Spectral Purity Filter with Recessed Multilayer Stack
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Solution Overview
Problem
Current spectral purity filters for EUV radiation systems in lithography are limited by their inability to withstand high heat loads, size constraints, and effectiveness in filtering out undesirable radiation, which affects the purity and durability of the radiation beam.
Innovation Solution
A spectral purity filter with a multilayer stack and recesses on a base substrate is designed to reflect EUV radiation while redirecting unwanted infrared and deep ultraviolet radiation, enhancing the spectral purity of the beam and improving the durability of the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spectral purity filters are used to filter non-EUV radiation, then spectral purity of the radiation beam is improved, but the filter cannot withstand high heat loads
Solution Approach 1:
The filter surface is segmented into multiple recesses that redirect different wavelengths to different locations, separating the EUV radiation path from the IR/NUV radiation path. This segmentation allows the filter to handle heat loads by directing unwanted radiation away from the optical path.
Solution Approach 2:
The unwanted IR and NUV radiation is extracted from the radiation beam by the recesses, which redirect these wavelengths to different locations. This extraction removes the harmful thermal load from the optical path while maintaining EUV radiation integrity.
2Reliability
If spectral purity filters are used to filter non-EUV radiation, then spectral purity of the radiation beam is improved, but the filter size is limited
Solution Approach 1:
The filter uses angular/directional separation in addition to wavelength filtering. By redirecting unwanted radiation at different angles through the recesses, the filter achieves spectral purity without requiring a larger physical size, as the separation occurs in the angular dimension rather than requiring increased filter area.
3Reliability
If spectral purity filters are used to filter non-EUV radiation, then spectral purity of the radiation beam is improved, but filtering effectiveness is insufficient
Solution Approach 1:
Different regions of the filter surface (different recesses) have different local qualities optimized for specific wavelength ranges. The recesses are configured with specific depths and geometries that provide enhanced filtering effectiveness for different out-of-band wavelengths, achieving superior overall spectral purity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively filters out unwanted radiation, maintaining the spectral purity of the EUV beam and ensuring the system's durability, even under high heat loads, thereby enhancing the capabilities of EUV lithography.
Implementation Method 1
A spectral purity filter is provided which is configured to reflect radiation having a first wavelength in a first direction and to reflect radiation having a second wavelength in a second direction that is different from the first direction
Implementation Method 2
The recesses are configured to allow the radiation having the first wavelength to be reflected in the first direction and to reflect the radiation having the second wavelength in the second direction
Data Source
AI summary
A radiation system is configured to generate a radiation beam. The radiation system comprising a chamber that includes a radiation source configured to generate radiation, a radiation beam emission aperture, and a radiation collector configured to collect radiation generated by the source, and to transmit the collected radiation to the radiation beam emission aperture. The radiation collector includes a spectral purity filter configured to enhance a spectral purity of the radiation to be emitted via the aperture.